Mushroom growing supplements have been prepared from cottonseed and soybean meals as described in U.S. Pat. No. 3,942,969. The meal is subjected to a protracted reaction with formaldehyde to denature the protein and thereby reduce its solubility and bio-availability. Several reaction procedures are described in the patent; namely, (1) vapor treatment, (2) liquid formaldehyde denaturing, and (3) low volume liquid formaldehyde denaturing.
For the vapor treatment, 37% aqueous formaldehyde was evaporated in an oven containing the supplement and equipped with a circulation fan. To denature two pounds of supplement, over three quarts of formaldehyde solution were vaporized in a period of 32 hours. The treated supplement was then dried for an additional sixteen hours.
In the liquid formaldehyde denaturing, the meal was mixed with 4% aqueous formaldehyde. The meal was allowed to stand in the solution for an hour with occasional stirring. Then the meal was dewatered, washed, and dried in trays at 212.degree. F. for 48 hours.
The low volume liquid formaldehyde denaturing procedure used a 10% aqueous formaldehyde solution which was mixed with the meal at the rate of 2.3 ounces of solution per pound of meal, then placed in airtight containers, and incubated at room temperature for 20 hours. Thereafter, the treated meal was dried in a vented oven at 212.degree. F. for 12 to 14 hours.
All of the foregoing procedures used large amounts of the formaldehyde treating solution and required lengthy treatment times for reaction completion. Further, the resulting products were wet meals, requiring dewatering or drying. A dry free-flowing product is desired for packaging and use by mushroom growers. In the prior art procedures, drying was also apparently necessary to remove excess unreacted formaldehyde from the treated meal.
Notwithstanding the difficulties and expense of preparing mushroom growing supplements by previously known procedures, such supplements have become an important product for use by mushroom growers in the United States. The formaldehyde-treated meals are added by most mushroom growers to the compost at the time of spawning. Some growers also add treated meal at the time of casing, preparatory to mushroom production.
The advantages obtained by using formaldehyde-treated meal supplements have been described. See, Randle (1983) Crop Research, 23(1):51-69. Among the reported advantages is that overheating of the compost during spawning is controlled, while providing protein nutrient for later use by the growing mushrooms. Also, the meal additive is protected from attack by other microorganisms until the mushroom mycelia become established. In addition, greater mushroom production per "flush" or "break" has been reported.
U.S. Pat. No. 3,942,969 mentions "corn gluten" together with many other kinds of vegetable and protein meals, for possible use in producing a mushroom supplement. However, as far as is known, corn gluten meal has not been used commercially or ever tested experimentally as a mushroom growing supplement. Prior to the present invention, the potential advantages of corn gluten meal over other vegetable meals does not appear to have been recognized.
Moreover, U.S. Pat. No. 3,942,969 advises that "only small amounts of sugars or starches can be tolerated" in mushroom supplements. Corn gluten meal can contain from 13 to 25% starch (dry basis), the more usual range being 16 to 22%.